The use of endoscopes for diagnostic and therapeutic indications is rapidly expanding. To improve performance,, endoscopes have been optimized to best accomplish their purpose. Therefore, there are upper endoscopes for examination of the esophagus, stomach and duodenum, colonoscopes for examining the colon, angioscopes for examining blood vessels, bronchoscopes for examining the bronchi, laparoscopes for examining the peritoneal cavity, and arthroscopes for examining joint spaces. All of these endoscopes have common problems which are addressed by the invention described and claimed herein.
Instruments to examine the rectum and sigmoid colon, known as flexible sigmoidoscopes, are good examples of the usefulness of endoscopes and the need for improvements to make such endoscopes so that they can be easily and quickly cleaned and disinfected. Flexible sigmoidoscopes are expensive, used in a contaminated environment for a procedure which is relatively brief and where problems of cleaning time and contamination are important factors. There has been a large increase in the use of the flexible sigmoidoscope for use in screening symptomatic and asymptomatic patients for colon and rectal cancer. Ideally, flexible sigmoidoscopes must be used rapidly and inexpensively in order to maintain the process of screening at acceptable levels. For example, many clinics would like to perform five to ten sigmoidoscope examinations each hour. One significant problem with making such examinations quick and inexpensive is the time necessary for adequately cleaning the device.
Although endoscopes can be cleaned in about two to four minutes, this relatively cursory cleaning may not be adequate for complete disinfection or sterilization. Even a more complete cleaning requiring on the order of eight to ten minutes may not allow adequate cleaning, particularly in view of the increasing problems with contagious viruses. Even with the use of chemicals such as glutaraldehyde, adequate cleanliness may not always be possible.
While the external surfaces of endoscopes can often be adequately cleaned, endoscopes typically have air, water, biopsy and suction channels extending along their lengths which come into contact with body tissues. Although these channels can be cleaned to some extent, it is very difficult to adequately clean valves for regulating the flow of fluid through these channels as well as various fittings and other components that come into contact with fluids flowing through the channels. If an inexpensive technique could be devised to prevent contamination of these valves, fittings and other components, the difficulty of cleaning endoscopes would not be so acute. For example, if the valves, fittings and channels did not become contaminated, then it would be possible to clean the channels themselves, as well as the external surfaces of the endoscope, with relatively less time and with a much greater degree of assurance that the endoscope is not contaminated by viruses and bacteria after it has been cleaned and disinfected.
Even if endoscopes can be adequately cleaned in eight to ten minutes, the cleaning still prevents endoscopic examinations from being relatively inexpensive. While a physician may spend five to ten minutes performing the endoscopy, he or she will generally waste a great deal of time waiting for the endoscope to be cleaned before he or she can conduct another endoscopic procedure. A partial solution to this "idle time" problem is to purchase multiple instruments so one can be used as the others are being cleaned. However, the expense of having duplicate endoscopes of each type makes this solution impractical, especially for physicians' offices and smaller clinics.
Not only must the idle time of the physician be added to the cost of endoscopy examinations, but the time spent by a nurse or other hospital personnel in the cleaning, as well as the cost of disinfecting chemicals, must be added to the cost of the examination. Although washing machines are available to clean endoscopes, these machines are expensive and not significantly faster than washing by hand. As a result, with conventional endoscopic procedures, both the physician and the relatively expensive endoscope presently have a down time approaching 50%.
One approach to the endoscope contamination problem is described and claimed in U.S. Pat. No. 4,646,722 to Silverstein et al. The Silverstein et al. patent discloses the use of a flexible rubber sheath that surrounds the insertion tube of an endoscope. The distal end of the sheath includes a transparent window that covers the viewing window of an endoscope. The sheath may also include a channel that extends along the insertion tube to allow endoscopic procedures to be performed without contaminating the endoscope itself. Once a procedure has been completed, the sheath, including its channel, is removed from the endoscope thus leaving the endoscope free to perform additional procedures without cleaning or disinfecting. The approach described in the Silverstein et al. patent has provided a great improvement in the ability to conduct endoscopic procedures without either the risk of contamination or the expense of thorough cleaning and disinfecting between procedures. However, the approach described in the Silverstein et al. patent requires a new sheath and channel for each procedure since the sheath is discarded after it used in performing an endoscopic procedure.
One area of conventional endoscopes that is particularly difficult to clean and disinfect is the distal end of the endoscope insertion tube. The distal end of most insertion tubes include not only viewing and lighting windows, but they also include air or water nozzles which, because they are formed by close-fitting surfaces, are very difficult to clean. If a technique could be found to easily clean and disinfect the components mounted at the distal end of the endoscope, as well as the valves for the fluid passages, the remainder of the endoscope could be cleaned and disinfected with relative ease and relatively little expense.